Finasteride for Male Androgenetic Alopecia – Evidence‑Based Guideline Summary

Safety: Sexual Adverse Effects

Approximately 2–4 % of men taking finasteride 1 mg daily experience sexual side effects (erectile dysfunction, decreased libido, reduced ejaculate volume, or gynecomastia) — the absolute increase over placebo is about 1–2 %【6】【7】.
On a 0–100 sexual‑function scale, finasteride produces a mean difference of 3.21 points, which is smaller than the 1.26‑point decline associated with each additional year of age【6】【7】.
Discontinuation due to adverse events occurs in 6–7 % of patients, a rate comparable with placebo【6】【7】.

Finasteride reduces serum PSA by ~50 % after 12 months of therapy【6】【7】.
After 3 years of continuous use, PSA suppression exceeds 50 % and a multiplication factor of 2.3 should be applied to measured PSA values for accurate prostate‑cancer risk assessment【6】【7】.

The only evidence‑based dose for male androgenetic alopecia is finasteride 1 mg taken orally once daily; higher doses (2.5 mg, 5 mg) lack supporting data for hair‑loss treatment and increase unnecessary risk【6】【7】.

Finasteride is teratogenic to male fetuses, causing abnormalities such as hypospadias, reduced anogenital distance, and delayed preputial separation【8】【9】【10】.
Women who could become pregnant must use reliable contraception throughout therapy and for at least 30 days after stopping finasteride【8】【9】【10】.